The present invention relates to a magnetic disk drive, and more particularly to a magnetic disk drive having an efficient layout of circuit elements on a circuit board.
Devices using various types of media such as optical disks and magnetic tapes are known in the art as recording media drives provided in the interior or the exterior of information processing apparatuses. Among them, hard disk drives (hereinafter referred to as HDDs) have become popular as storage devices for information processing apparatuses to such an extent that they are one type of the storage devices indispensable for today's information processing systems. Further, not limited to the information processing apparatuses as described above, HDDs are expanding more and more in application. For example, HDDs are used for moving picture recording/reproducing devices, car navigation systems, cellular phones, and removable memories for use in them.
Each magnetic disk used in HDDs has a plurality of tracks formed concentrically and each track is partitioned into a plurality of sectors. Sector address information and user data are stored in each sector. Either data write to a sector or data read from the sector is enabled by a magnetic head which accesses the desired sector according to the sector address information. A signal read out by the head from a magnetic disk through data read operation is subjected to waveform shaping, decoding processing and other prescribed signal processing by a signal processing circuit disposed on an HDD circuit board before being transmitted to the host. Likewise, data transferred from the host is subjected to prescribed signal processing by the signal processing circuit and then written to the magnetic disk.
Reducing the size of the HDD has heretofore been performed. For example, what is called a one inch type HDD (also called a 1.0 type HDD) using a magnetic disk of 26 to 28 mm in diameter) and a smaller size of a 0.85 inch type HDD have appeared on the market. These small-sized HDDs are implemented not only by the reduction in size of magnetic disks but also by the reduction in size of mechanical parts such as a spindle motor (SPM), an actuator, and a voice coil motor (VCM) and of signal processing circuits such as a hard disk controller (HDC) mounted on a circuit board.
Further, apertures are formed in a circuit board so as to thin these small-sized HDDs. Protrusions, which are formed on a housing for accommodating rotary shafts of SPM and actuator, are fitted in the apertures formed in the circuit board to complete assembly.